What is a landspout and how is it different from a tornado?
The landspout, or non supercell tornado, is a different breed of tornado. The formation of a non-supercell tornado is similar to that of a waterspout. They form as winds swirl at the surface, similar to a dust devil. As an updraft builds, this swirling air can be pulled up into the updraft. As this occurs, the swirling air is stretched and tightened, which causes the rotating winds to increase in speed, similar to the way a figure skater pulls her arms in close to her body as she spins and the spin becomes faster.
See the video of the landspout below...
Video of landspout on the Nuevo Laredo-Monterrey Highway in Mexico posted to YouTube user Melissa Estrada on March 29
Wikipedia offers some additional detail on these unconventional twisters:
Known officially as “dust-tube tornadoes” by the National Weather Service, they form during the growth stage of convective clouds by the ingestion and tightening of boundary layer vorticity [spin] by the cumuliform tower’s updraft. Landspouts most often occur in drier areas with high-based storms and considerable low-level instability. They generally are smaller and weaker than supercellular tornadoes, though many persist in excess of 15 minutes and some have produced F3 damage.